Model, View, Constraints and Tests for Product Codes #596

This module implments a O2M in product to product.code which adds a functionality
to add EAN/UPC-A/Other codes to product. EAN and UPC-A have basic length check constraints.
Also allows search within code as well when a search on product is done
Add xmltests command to setup.py to support CI with coverage and xunit reports #596
Merge pull request #1 from shalabhaggarwal/develop

Model, View, Constraints and Tests for Product Codes #596